At the present time, fabrication of optical waveguides is achieved by either a polymer spin-on technique or a diffusion technique, both of which require expensive photolithography steps. Additionally, both fabrication techniques are ineffective and inefficient for fabricating optical waveguides in high volumes for several reasons, such as complex processing steps, difficulties in controlling the processing steps, and high cost.
In U.S. Pat. No. 5,265,184, entitled "Molded Waveguide and Method For Making Same", issued Nov. 23, 1993, new molded waveguides are disclosed which are fabricated by molding upper and lower cladding layers with grooves defined therebetween. Optical waveguides are formed by filling the grooves with an optically clear adhesive which forms the core of the optical waveguide and simultaneously fixes the upper and lower cladding layers together.
One problem which arises with the molded optical waveguide described in the '184 Patent is the filling of the grooves without introducing bubbles into the liquid adhesive. If an air bubble is formed in the liquid adhesive and the air bubble remains in the groove after fixing the upper and lower cladding layers together, the core of the waveguide will not conduct light properly.
Also, since the upper and lower cladding layers surround the core and form the optical waveguide in conjunction with the core, the upper and lower cladding layers are generally molded from optical quality, transparent epoxies or the like which have a refractive index slightly lower than the refractive index of the core. Thus, to provide the optimum efficiency the upper and lower cladding layers are formed of relatively expensive plastic material.
Therefore, an optical waveguide which could be fabricated by utilizing a cheaper plastic material in the bulk volumes would be highly desirable.
It is a purpose of the present invention to provide a new and improved optical waveguide.
It is another purpose of the present invention to provide a new and improved optical waveguide which is less expensive.
It is still another purpose of the present invention to provide a new and improved optical waveguide which is simple and efficient to fabricate.
It is a further purpose of the present invention to provide a new and improved optical waveguide which can be easily incorporated into other molding processes.